WO 2006/111335 A1 discloses a system for supplying a load with electric energy comprising a hydrogen evolution device that releases hydrogen when an electric current flows through. The device is coupled to a fuel cell unit in which hydrogen generated by the hydrogen evolution device can be reacted with an oxidant. The fuel cell unit and the hydrogen evolution device electrically connect in series so that under load the essentially equal current amount flows through the fuel cell unit and the hydrogen evolution device. The hydrogen evolution device preferably comprises button cell-shaped hydrogen evolution cells, as described in DE 35 32 335 A1, for example.
A frequent problem with such systems is that fuel cells have a very high electric resistance which is why starting such a system can be very slow. According to WO 2006/111335 A1, this is counteracted in that a parallel circuit to the fuel cell unit is provided, via which, when connecting a load, an electric current can flow from the hydrogen evolution device bypassing the fuel cell unit. Thus, when switching on the load, current can flow through the hydrogen evolution device unhindered by the high electric resistance of the fuel cell unit. As a result, hydrogen evolution starts within the latter which in turn causes a more rapid activation of the fuel cell units. Thus, a significantly faster system start is achieved than would be the case without the parallel circuit.
In any event, the progress of the start of such a system still may be comparatively slow, for example, as compared to a battery. In particular in the case of low starting temperatures (below 0° C.) it can under certain circumstances take multiple seconds until the system provides its nominal voltage despite the parallel circuit.